Known as one of techniques for production of a strip directly from molten metal is twin-roll continuous casting where the molten metal is supplied between a pair of chilled rolls arranged horizontally to deliver the solidified metal as a strip.
FIG. 5 shows an example of such twin roll caster comprising a pair of chilled rolls 1 arranged horizontally and a pair of side weirs 2 associated with the rolls 1.
The chilled rolls 1 with cooling water passing therethrough are constructed such that a nip G between the rolls may be adjusted to be increased/decreased depending on thickness of the strip 3 to be produced.
Rotational directions and velocities of the chilled rolls 1 are set such that outer peripheries of the rolls 1 are moved from above toward the nip G at constant velocity.
One and the other of the side weirs 2 surface-contact one and the other ends of the chilled rolls 1, respectively. In a space defined by the chilled rolls 1 and the side weirs 2, a molten metal supply nozzle 4 made of refractory material is arranged to be positioned just above the nip G between the rolls.
The molten metal supply nozzle 4 has an elongated top nozzle trough 6 for reception of molten metal 5 and has longitudinal side walls each formed with openings 7 adjacent to a lower end of the nozzle and extending from the trough 6 toward outer peripheries of the chilled rolls 1, the openings 7 being aligned along axes of the rolls 1. Thus, the molten metal 5 is poured into the nozzle trough 6 to form a molten metal pool 8 above the nip G between the chilled rolls 1 and in contact with the outer peripheries of the rolls 1.
Thus, with the molten metal pool 8 being formed, the chilled rolls 1 are rotated while being cooled by passing of the cooling water therethrough, so that the molten metal 5 is solidified on the outer peripheries of the rolls 1 into shells which are brought together at the nip G into the strip 3 which in turn is delivered downwardly from the rolls 1.
In this case, in order that the strip 3 produced may have a target thickness, horizontal pushing forces are applied to bearing chocks (not shown) for support of necks on the respective chilled rolls 1 in directions toward each other.
When oxides of, for example, the molten metal 5 adhere to the outer peripheries of the chilled rolls 1 in the molten metal pool 8, an effect of cooling the solidified shells at oxides-adhering regions becomes insufficient and cracks may develop on the surfaces of the strip 3.
In order to overcome this, there has been proposed a roll brushing device with brush rolls facing the outer peripheries of the chilled rolls 1 over axial lengths thereof, respectively. While being rotated by motors, the brush rolls are pushed against the chilled rolls 1 to wipe off the oxides adhering to the outer peripheries of the rolls 1 (see, for example, Patent Literature 1).
In Patent Literature 1, speaking exaggeratingly, in complementary with the chilled rolls 1 hourglass-shaped or having axially opposite ends greater in outer diameter than axially intermediate portions, the brush rolls are barrel-shaped or have axially opposite ends smaller in outer diameter than axially intermediate portions (difference in outer diameter between the axially opposite ends and the axially intermediate portions in the chilled rolls 1 or in the brush rolls is of the order of 0.4 mm).
[Patent Literature 1] JP 6-114507A